MAK (male germ cell-associated kinase) is a serine/threonine protein kinase of the RCK group of the CMGC family, closely related to CILK1 (ICK) and MOK. Like ICK, it is activated by dual phosphorylation of a TDY motif, through autophosphorylation and phosphorylation by CDK20 (CCRK). MAK is highly expressed in testis and in retinal photoreceptors. In photoreceptors it localizes to the connecting cilium and outer-segment axoneme (mouse) and to the inner segment (human), where it restrains ciliary length: Mak-null mouse photoreceptors have elongated cilia with accumulated IFT88/IFT57 and progressive degeneration, and MAK phosphorylates the axonemal protein RP1, whose overexpression-induced ciliary elongation MAK suppresses. Homozygous loss of the retina-specific MAK isoform (e.g., an exon 9 Alu insertion) causes autosomal recessive retinitis pigmentosa. In prostate cancer cells MAK has been reported to act as an androgen receptor coactivator and, during mitosis, to associate with spindle, centrosomes and midbody and phosphorylate CDH1/FZR1.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0001750 photoreceptor outer segment | IEA GO_REF:0000120 | ACCEPT | Summary: Photoreceptor outer segment transferred from mouse. Reason: Mouse Mak localizes to outer-segment axonemes; human immunohistochemistry detected MAK mainly in inner segments and not distal to the connecting cilium, so the outer-segment pool may be species- or antibody-dependent. Supporting Evidence: PMID:21148103 Mak was localized both in the connecting cilia and outer-segment axonemes of photoreceptor cells. |
| GO:0001750 photoreceptor outer segment | ISS GO_REF:0000024 | ACCEPT | Summary: Photoreceptor outer segment (ISS from mouse). Reason: As above. Supporting Evidence: PMID:21148103 Mak was localized both in the connecting cilia and outer-segment axonemes of photoreceptor cells. |
| GO:0001917 photoreceptor inner segment | IDA PMID:21825139 Exome sequencing and analysis of induced pluripotent stem ce... | ACCEPT | Summary: MAK in inner segments of human rod and cone photoreceptors. Reason: Direct immunohistochemistry of human retina. Supporting Evidence: PMID:21825139 Immunohistochemistry of human donor tissue revealed that MAK is expressed in the inner segments, cell bodies, and axons of rod and cone photoreceptors. |
| GO:0001917 photoreceptor inner segment | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt: photoreceptor inner segment. Reason: As above. Supporting Evidence: PMID:21825139 Immunohistochemistry of human donor tissue revealed that MAK is expressed in the inner segments, cell bodies, and axons of rod and cone photoreceptors. |
| GO:0003713 transcription coactivator activity | IDA PMID:16951154 Male germ cell-associated kinase, a male-specific kinase reg... | KEEP AS NON CORE | Summary: MAK acts as an androgen receptor coactivator in prostate cancer cells. Reason: Experimental (co-IP, reporter, shRNA) support in prostate cancer cell lines; the physiological relevance in normal tissue is unclear and MAK is not a canonical transcriptional coregulator. Retained as non-core. Supporting Evidence: PMID:16951154 In this study, we describe the characterization of a novel protein kinase, male germ cell-associated kinase (MAK), which serves as a coactivator of AR. PMID:16951154 MAK physically associates with AR (MAK and AR are found to be coprecipitated from cell extracts, colocalized in nucleus, and corecruited to prostate-specific antigen promoter in LNCaP as well as in transfected cells) |
| GO:0004672 protein kinase activity | IEA GO_REF:0000120 | ACCEPT | Summary: InterPro/ARBA: protein kinase activity. Reason: Consistent with direct kinase assays. Supporting Evidence: PMID:21986944 Wild-type MAK strongly phosphorylated MBP in vitro (Figure 3B upper), and exhibited autophosphorylation on the TDY motif in vivo as detected by antibody that specifically recognizes the dual-phosphorylated TXY (Figure 3B lower). |
| GO:0004672 protein kinase activity | NAS PMID:2183027 A novel mammalian protein kinase gene (mak) is highly expres... | ACCEPT | Summary: Protein kinase activity predicted at cloning (rat). Reason: Later confirmed experimentally. Supporting Evidence: PMID:2183027 the predicted product of rat mak consisted of 622 amino acids and contained protein kinase consensus motifs in its amino-terminal region. PMID:12084720 When expressed in COS1 cells, hMAK is kinase-active as demonstrated by autophosphorylation and phosphorylation of exogenous substrate and is localized in the nucleus. |
| GO:0004674 protein serine/threonine kinase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA: protein serine/threonine kinase activity. Reason: Core activity. Supporting Evidence: PMID:21986944 Wild-type MAK strongly phosphorylated MBP in vitro (Figure 3B upper), and exhibited autophosphorylation on the TDY motif in vivo as detected by antibody that specifically recognizes the dual-phosphorylated TXY (Figure 3B lower). file:human/MAK/MAK-deep-research-falcon.md MAK catalyzes ATP-dependent phosphorylation of protein serine/threonine residues. |
| GO:0004674 protein serine/threonine kinase activity | IEA GO_REF:0000003 | ACCEPT | Summary: EC 2.7.11.1 mapping. Reason: Core activity. Supporting Evidence: PMID:21148103 Interestingly, we found that GST-RP1-N was markedly phosphorylated by Mak, whereas no obvious phosphorylation of the GST-RP1 C-terminal (GST-RP1-C1) construct or GST alone was detected ( Fig. |
| GO:0005515 protein binding | IPI PMID:16951154 Male germ cell-associated kinase, a male-specific kinase reg... | MODIFY | Summary: MAK co-precipitates with androgen receptor (P10275). Reason: The interaction is with a nuclear receptor and underlies the reported coactivator activity; nuclear androgen receptor binding is the informative term. Proposed replacements: nuclear androgen receptor binding Supporting Evidence: PMID:16951154 MAK physically associates with AR (MAK and AR are found to be coprecipitated from cell extracts, colocalized in nucleus, and corecruited to prostate-specific antigen promoter in LNCaP as well as in transfected cells) |
| GO:0005515 protein binding | IPI PMID:21986944 Male germ cell-associated kinase is overexpressed in prostat... | REMOVE | Summary: MAK interacts with CCRK/CDK20 (Q8IZL9), which phosphorylates its TDY motif. Reason: Generic protein binding; the functional relationship (CDK20 as upstream activating kinase of MAK) is an activity of CDK20, not of MAK. Removal does not imply the interaction is false. Supporting Evidence: PMID:21986944 This dual phosphorylation of MAK in vivo was enhanced by overexpression of CCRK (Figure 3C), which also physically interacted with MAK (Figure 3D). |
| GO:0005515 protein binding | IPI PMID:21986944 Male germ cell-associated kinase is overexpressed in prostat... | REMOVE | Summary: MAK binds and phosphorylates CDH1/FZR1 (Q9UM11). Reason: Generic protein binding; the informative aspect (CDH1 as kinase substrate) is covered by kinase activity annotations. Removal does not imply the interaction is false. Supporting Evidence: PMID:21986944 MAK associates with CDH1 (FZR1, fizzy/cell division cycle 20 related 1) and phosphorylates CDH1 at sites phosphorylated by cyclin-dependent kinases. |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro: ATP binding. Reason: Correct for a protein kinase. Supporting Evidence: PMID:21986944 Wild-type MAK strongly phosphorylated MBP in vitro (Figure 3B upper), and exhibited autophosphorylation on the TDY motif in vivo as detected by antibody that specifically recognizes the dual-phosphorylated TXY (Figure 3B lower). |
| GO:0005634 nucleus | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA: nucleus (CMGC kinases). Reason: Overexpressed MAK is nuclear and HPA detects nucleoplasm, but the best-characterized physiological role is ciliary. Supporting Evidence: PMID:12084720 When expressed in COS1 cells, hMAK is kinase-active as demonstrated by autophosphorylation and phosphorylation of exogenous substrate and is localized in the nucleus. |
| GO:0005634 nucleus | IDA PMID:12084720 Identification of human male germ cell-associated kinase, a ... | KEEP AS NON CORE | Summary: Overexpressed hMAK is nuclear. Reason: As above. Supporting Evidence: PMID:12084720 When expressed in COS1 cells, hMAK is kinase-active as demonstrated by autophosphorylation and phosphorylation of exogenous substrate and is localized in the nucleus. |
| GO:0005634 nucleus | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt: nucleus. Reason: As above. Supporting Evidence: PMID:12084720 When expressed in COS1 cells, hMAK is kinase-active as demonstrated by autophosphorylation and phosphorylation of exogenous substrate and is localized in the nucleus. |
| GO:0005654 nucleoplasm | IDA GO_REF:0000052 | KEEP AS NON CORE | Summary: HPA immunofluorescence: nucleoplasm. Reason: Antibody-based call; image not inspected. Supporting Evidence: PMID:12084720 When expressed in COS1 cells, hMAK is kinase-active as demonstrated by autophosphorylation and phosphorylation of exogenous substrate and is localized in the nucleus. |
| GO:0005730 nucleolus | IDA GO_REF:0000052 | KEEP AS NON CORE | Summary: HPA immunofluorescence: nucleolus. Reason: Antibody-based call without functional context; image not inspected. |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: IBA: cytoplasm. Reason: Correct broad location. Supporting Evidence: PMID:21825139 Immunohistochemistry of human donor tissue revealed that MAK is expressed in the inner segments, cell bodies, and axons of rod and cone photoreceptors. |
| GO:0005813 centrosome | IDA PMID:21986944 Male germ cell-associated kinase is overexpressed in prostat... | ACCEPT | Summary: MAK associates with centrosomes in mitosis. Reason: Centrosomal localization in dividing cells; consistent with the HPA basal body call (Approved) in ciliated cells. Supporting Evidence: PMID:21986944 At metaphase and anaphase, MAK associates with the mitotic spindle and centrosomes (Figure 2B). |
| GO:0005813 centrosome | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt: centrosome. Reason: As above. Supporting Evidence: PMID:21986944 At metaphase and anaphase, MAK associates with the mitotic spindle and centrosomes (Figure 2B). |
| GO:0005819 spindle | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt: spindle. Reason: Mitotic spindle association reported in prostate cancer cells; peripheral. Supporting Evidence: PMID:21986944 At metaphase and anaphase, MAK associates with the mitotic spindle and centrosomes (Figure 2B). |
| GO:0005929 cilium | IBA GO_REF:0000033 | ACCEPT | Summary: IBA: cilium (RCK kinases). Reason: Supported by photoreceptor connecting cilium/axoneme localization. Supporting Evidence: PMID:21148103 Mak was localized both in the connecting cilia and outer-segment axonemes of photoreceptor cells. |
| GO:0005930 axoneme | IEA GO_REF:0000107 | ACCEPT | Summary: Axoneme transferred from mouse. Reason: Mak localizes to outer-segment axonemes in mouse. Supporting Evidence: PMID:21148103 Mak was localized both in the connecting cilia and outer-segment axonemes of photoreceptor cells. |
| GO:0006468 protein phosphorylation | IDA PMID:21986944 Male germ cell-associated kinase is overexpressed in prostat... | ACCEPT | Summary: MAK phosphorylates CDH1 and MBP. Reason: Correct process for a protein kinase. Supporting Evidence: PMID:21986944 MAK associates with CDH1 (FZR1, fizzy/cell division cycle 20 related 1) and phosphorylates CDH1 at sites phosphorylated by cyclin-dependent kinases. |
| GO:0007283 spermatogenesis | NAS PMID:2183027 A novel mammalian protein kinase gene (mak) is highly expres... | MARK AS OVER ANNOTATED | Summary: Spermatogenesis inferred from testis-specific expression (rat). Reason: The claim rests on expression in meiotic and post-meiotic germ cells; the cited work does not test a role in spermatogenesis, and no functional evidence was found in the reviewed literature. Supporting Evidence: PMID:2183027 These results suggest that the mak gene plays an important role in spermatogenesis. |
| GO:0030496 midbody | IDA PMID:21986944 Male germ cell-associated kinase is overexpressed in prostat... | KEEP AS NON CORE | Summary: MAK at the midbody from anaphase to telophase. Reason: Observed in dividing prostate cancer cells; peripheral. Supporting Evidence: PMID:21986944 At anaphase MAK also locates to the midbody and remained in this locale until telophase (Figure 2B bottom, 2C). |
| GO:0030496 midbody | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt: midbody. Reason: As above. Supporting Evidence: PMID:21986944 At anaphase MAK also locates to the midbody and remained in this locale until telophase (Figure 2B bottom, 2C). |
| GO:0031514 motile cilium | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Motile cilium transferred from mouse. Reason: Possibly reflects sperm flagellum expression; Mak loss does not alter respiratory motile cilia length, so its established role is in photoreceptor (non-motile) cilia. Supporting Evidence: PMID:21148103 However, the ciliary length of respiratory epithelia did not differ in wild-type and Mak -KO mice ( Fig. |
| GO:0032391 photoreceptor connecting cilium | IEA GO_REF:0000107 | ACCEPT | Summary: Photoreceptor connecting cilium transferred from mouse. Reason: Core location. Supporting Evidence: PMID:21148103 Mak was localized both in the connecting cilia and outer-segment axonemes of photoreceptor cells. PMID:21825139 MAK encodes a kinase involved in the regulation of photoreceptor-connecting cilium length. |
| GO:0035556 intracellular signal transduction | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA: intracellular signal transduction (CMGC family). Reason: Family-level inference; no MAK-specific signalling pathway defined. Supporting Evidence: PMID:21986944 We found that MAK kinase activity requires dual phosphorylation of the conserved TDY motif and that the phosphorylation is dynamic during cell cycle. |
| GO:0042073 intraciliary transport | IBA GO_REF:0000033 | ACCEPT | Summary: IBA: intraciliary transport (RCK kinases). Reason: IFT88 and IFT57 accumulate in Mak-null photoreceptor axonemes and IFT components concentrate at connecting-cilium tips; Mak is a tip-localized IFT regulator acting with Ick. Supporting Evidence: PMID:21148103 Notably, in Mak -KO photoreceptors, we found that IFT88 and IFT57 were accumulated in outer-segment axonemes ( Fig. PMID:39293864 Here, we identified that the ciliopathy kinase Mak is a ciliary tip-localized IFT regulator that cooperatively acts with the ciliopathy kinase Ick, an IFT regulator. PMID:39293864 IFT components were concentrated at the tips of photoreceptor connecting cilia in the Mak−/− retina (arrowheads). |
| GO:0045494 photoreceptor cell maintenance | IEA GO_REF:0000107 | ACCEPT | Summary: Photoreceptor cell maintenance transferred from mouse. Reason: Mak-null photoreceptors degenerate and MAK loss causes human RP. Supporting Evidence: PMID:21148103 In the Mak -null retina, photoreceptors exhibit elongated cilia and progressive degeneration. PMID:21825139 We used exome sequencing to identify a homozygous Alu insertion in exon 9 of male germ cell-associated kinase (MAK) as the cause of disease in an isolated individual with RP. |
| GO:0045494 photoreceptor cell maintenance | ISS GO_REF:0000024 | ACCEPT | Summary: Photoreceptor cell maintenance (ISS from mouse). Reason: As above. Supporting Evidence: PMID:21148103 Our observations in the Mak -KO retina suggest that a negative regulatory mechanism of ciliary length is essential for long-term photoreceptor survival, suggesting that this mechanism is involved in the pathogenesis of human photoreceptor degenerative diseases such as retinitis pigmentosa, Leber's congenital amaurosis, and BBS. |
| GO:0045893 positive regulation of DNA-templated transcription | IEA GO_REF:0000108 | KEEP AS NON CORE | Summary: Positive regulation of transcription inferred from coactivator activity. Reason: Follows from the AR coactivator data in prostate cancer cells; non-core. Supporting Evidence: PMID:16951154 In this study, we describe the characterization of a novel protein kinase, male germ cell-associated kinase (MAK), which serves as a coactivator of AR. |
| GO:0046777 protein autophosphorylation | IMP PMID:21986944 Male germ cell-associated kinase is overexpressed in prostat... | ACCEPT | Summary: MAK autophosphorylates its TDY motif. Reason: Direct evidence; part of activation mechanism. Supporting Evidence: PMID:21986944 Wild-type MAK strongly phosphorylated MBP in vitro (Figure 3B upper), and exhibited autophosphorylation on the TDY motif in vivo as detected by antibody that specifically recognizes the dual-phosphorylated TXY (Figure 3B lower). |
| GO:0060271 cilium assembly | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA: cilium assembly (RCK kinases). Reason: MAK is not required to build cilia; its loss elongates photoreceptor cilia. Its role is length restriction, captured by a proposed negative regulation of non-motile cilium assembly annotation. Supporting Evidence: PMID:21148103 In the Mak -null retina, photoreceptors exhibit elongated cilia and progressive degeneration. |
| GO:0072686 mitotic spindle | IDA PMID:21986944 Male germ cell-associated kinase is overexpressed in prostat... | KEEP AS NON CORE | Summary: MAK associates with the mitotic spindle. Reason: Peripheral, cancer-cell observation. Supporting Evidence: PMID:21986944 At metaphase and anaphase, MAK associates with the mitotic spindle and centrosomes (Figure 2B). |
| GO:0106310 protein serine kinase activity | EXP PMID:12084720 Identification of human male germ cell-associated kinase, a ... | ACCEPT | Summary: Protein serine kinase activity. Reason: Correct. Supporting Evidence: PMID:12084720 When expressed in COS1 cells, hMAK is kinase-active as demonstrated by autophosphorylation and phosphorylation of exogenous substrate and is localized in the nucleus. |
| GO:0106310 protein serine kinase activity | EXP PMID:21986944 Male germ cell-associated kinase is overexpressed in prostat... | ACCEPT | Summary: Protein serine kinase activity (CDH1/MBP phosphorylation). Reason: Correct. Supporting Evidence: PMID:21986944 Wild-type MAK strongly phosphorylated MBP in vitro (Figure 3B upper), and exhibited autophosphorylation on the TDY motif in vivo as detected by antibody that specifically recognizes the dual-phosphorylated TXY (Figure 3B lower). |
| GO:0106310 protein serine kinase activity | IEA GO_REF:0000116 | ACCEPT | Summary: Rhea-based protein serine kinase activity. Reason: Correct. Supporting Evidence: PMID:21986944 Wild-type MAK strongly phosphorylated MBP in vitro (Figure 3B upper), and exhibited autophosphorylation on the TDY motif in vivo as detected by antibody that specifically recognizes the dual-phosphorylated TXY (Figure 3B lower). |
| GO:0097542 ciliary tip | ISS PMID:39293864 Ccrk-Mak/Ick signaling is a ciliary transport regulator esse... | NEW | Summary: Proposed NEW annotation. Mouse Mak localizes to the tips of photoreceptor cilia and cultured-cell cilia, where it regulates IFT turnaround with Ick. Reason: The tip is the site of the IFT-turnaround regulation that underlies MAK length control; loss of Mak concentrates IFT components at connecting-cilium tips. Evidence is from the mouse ortholog (ISS); human retina immunostaining did not resolve a tip pool, and HPA calls basal body in cultured cells, so the tip location is best supported in photoreceptors. Supporting Evidence: PMID:39293864 Here, we identified that the ciliopathy kinase Mak is a ciliary tip-localized IFT regulator that cooperatively acts with the ciliopathy kinase Ick, an IFT regulator. PMID:39293864 IFT components were concentrated at the tips of photoreceptor connecting cilia in the Mak−/− retina (arrowheads). |
| GO:1902856 negative regulation of non-motile cilium assembly | ISS PMID:21148103 Negative regulation of ciliary length by ciliary male germ c... | NEW | Summary: Proposed NEW annotation. Mak restrains photoreceptor cilium length; Mak-null photoreceptor cilia are elongated. Reason: The mouse ortholog carries this term by IMP/IDA/IGI from the same study. Participation: MAK itself phosphorylates ciliary substrates (RP1) and suppresses RP1-induced elongation, so it performs the regulatory step. Human genetics (MAK-associated RP; MAK described as regulating connecting-cilium length) supports conservation. GO lacks a cilium-length term; this is the standard representation. Supporting Evidence: PMID:21148103 Here we show that male germ cell-associated kinase (Mak) regulates retinal photoreceptor ciliary length and subcompartmentalization. PMID:21148103 In the Mak -null retina, photoreceptors exhibit elongated cilia and progressive degeneration. PMID:21148103 Interestingly, we found that GST-RP1-N was markedly phosphorylated by Mak, whereas no obvious phosphorylation of the GST-RP1 C-terminal (GST-RP1-C1) construct or GST alone was detected ( Fig. PMID:21825139 MAK encodes a kinase involved in the regulation of photoreceptor-connecting cilium length. |
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Download this section (compressed HTML)Q: Does MAK regulate cilium length outside photoreceptors (e.g., in testis or in HPA-annotated basal bodies of cultured cells), or is its ciliary role photoreceptor-specific?
Q: Why does human retina immunostaining place MAK mainly in inner segments while mouse Mak is in the connecting cilium and outer-segment axoneme?
Q: Are the prostate-cancer AR coactivator and mitotic CDH1 functions relevant to normal physiology?
Experiment: Phosphoproteomics of wild-type versus MAK-null human iPSC-derived retinal organoids, with phosphosite mutant rescue scored by connecting-cilium and axoneme length.
Hypothesis: MAK phosphorylation of RP1 (and IFT/kinesin-2 substrates) controls photoreceptor axoneme length.
Type: Organoid phosphoproteomics and rescue
Experiment: Compare localization and length-control activity of MAK isoforms in photoreceptor-like cells.
Hypothesis: The retina-specific MAK isoform (exons 9 and 12) is required for ciliary localization.
Type: Isoform-specific localization and rescue
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